     (fn [feature]
       (update-in feature
                 :users
-                 #(conj % user)))))
+                 #(conj % (user-id user))))))
 
 (defn deactivate-user
   "deactivate a feature for a particular user"


;; functional core
(defrecord Feature [feature-name groups users percentage])

(defn parse-percentage [^String raw]
  (if (empty? raw)

    (fn [feature]
      (update-in feature
                 :users
                 #(disj % (user-id user))))))

(defn activate-percentage
  "activate a feature for a percentage of users.
